Scientists trying to put HIV-prevention methods in the hands of women have been disappointed so far in their efforts with vaginal microbicides. In the lab, in vitro testing of microbicides like nonoxynol-9, and cellulose sulfate have produced promising results, but when subjected to clinical trials, each of these compounds has failed miserably. Not only do nonoxynol-9, and cellulose sulfate fail to protect against HIV infection, when a woman uses the stuff frequently she actually has an increased risk of HIV infection.

Why the tragic paradox? Do microbicides like these change the vaginal microbiome? The authors of a paper in mBio this week tested whether products like these might impact the the microbial community of the vagina, an observation that might begin to explain why these microbicides don’t work on HIV in real-world conditions.